#include "userprog/process.h"
#include <debug.h>
#include <inttypes.h>
#include <round.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "userprog/gdt.h"
#include "userprog/pagedir.h"
#include "userprog/tss.h"
#include "filesys/directory.h"
#include "filesys/file.h"
#include "filesys/filesys.h"
#include "threads/flags.h"
#include "threads/init.h"
#include "threads/interrupt.h"
#include "threads/palloc.h"
#include "threads/thread.h"
#include "threads/vaddr.h"
#include "devices/timer.h"
#include "threads/synch.h"
#include "vm/frame.h"
#include "vm/page.h"

static thread_func start_process NO_RETURN;
static bool load(const char *cmdline, void (**eip)(void), void **esp);
static void push_argvii(char *words, void **esp);
static void push_string_argvii(char *str, void **esp);
static void push_align(void **esp);
static void push_argvi(char *words, void **esp, uint32_t *temp_esp, uint32_t *num_p);
static void push_address_argvi(void **esp, uint32_t *address);

/* Starts a new thread running a user program loaded from
   FILENAME.  The new thread may be scheduled (and may even exit)
   before process_execute() returns.  Returns the new process's
   thread id, or TID_ERROR if the thread cannot be created. */
tid_t process_execute(const char *file_name)
{
  char *fn_copy;
  tid_t tid;

  /* Make a copy of FILE_NAME.
     Otherwise there's a race between the caller and load(). */
  fn_copy = palloc_get_page(0);
  if (fn_copy == NULL)
    return TID_ERROR;

  strlcpy(fn_copy, file_name, PGSIZE);
  char *name = palloc_get_page(0);

  strlcpy(name, file_name, PGSIZE);
  char *tmp;
  name = strtok_r(name, " ", &tmp);

  struct file *file = filesys_open(name);

  //如果文件不存在，返回-1
  if (file == NULL)
  {
    return -1;
  }

  /* Create a new thread to execute FILE_NAME. */
  tid = thread_create(name, PRI_DEFAULT, start_process, fn_copy);
  if (tid == TID_ERROR)
    palloc_free_page(fn_copy);

  //创建成功之后，子进程去load，父进程阻塞（sema初始为0）
  sema_down(&(thread_current()->exec_sema));

  palloc_free_page(name);

  //如果子进程load失败，返回-1
  if (thread_current()->child_load_success == false)
  {
    return -1;
  }
  //一个子进程创建并判断完之后，把child_load_success恢复false，以防下一个子进程出错
  thread_current()->child_load_success = false;
  return tid;
}

/* A thread function that loads a user process and starts it
   running. */
static void
start_process(void *file_name_)
{
  char *file_name = file_name_;
  struct intr_frame if_;
  bool success;

  /* Initialize interrupt frame and load executable. */
  memset(&if_, 0, sizeof if_);
  if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
  if_.cs = SEL_UCSEG;
  if_.eflags = FLAG_IF | FLAG_MBS;

  // 初始化进程页表
  hash_init(&thread_current()->page_table, page_hash, page_less, NULL);

  success = load(file_name, &if_.eip, &if_.esp);

  /* If load failed, quit. */
  palloc_free_page(file_name);
  if (!success)
  {
    //通知父进程子进程load失败
    thread_current()->father->child_load_success = false;
    sema_up(&(thread_current()->father->exec_sema));

    thread_exit();
  }
  //通知父进程子进程load成功
  thread_current()->father->child_load_success = true;
  sema_up(&(thread_current()->father->exec_sema));
  /* Start the user process by simulating a return from an
     interrupt, implemented by intr_exit (in
     threads/intr-stubs.S).  Because intr_exit takes all of its
     arguments on the stack in the form of a `struct intr_frame',
     we just point the stack pointer (%esp) to our stack frame
     and jump to it. */
  asm volatile("movl %0, %%esp; jmp intr_exit"
               :
               : "g"(&if_)
               : "memory");
  NOT_REACHED();
}

/* Waits for thread TID to die and returns its exit status.  If
   it was terminated by the kernel (i.e. killed due to an
   exception), returns -1.  If TID is invalid or if it was not a
   child of the calling process, or if process_wait() has already
   been successfully called for the given TID, returns -1
   immediately, without waiting.

   This function will be implemented in problem 2-2.  For now, it
   does nothing. */
int process_wait(tid_t child_tid)
{
  // timer_sleep(1000);
  struct thread *child = NULL;
  /* 遍历当前线程打开的文件，查找fd匹配的文件 */
  struct list_elem *e;
  struct thread *temp;
  for (e = list_begin(&thread_current()->child_threads); e != list_end(&thread_current()->child_threads); e = list_next(e))
  {
    temp = list_entry(e, struct thread, wait_elem);
    if (temp != NULL && child_tid == temp->tid)
    {
      child = temp;
      break;
    }
  }
  //如果不是直系子进程或者子进程已经被等待过
  if (child == NULL || child->is_waited)
  {
    return -1;
  }
  //如果子进程未被等待过，更改is_waited为true，开始wait
  child->is_waited = true;
  //将父进程阻塞在子进程的wait_sema上，不能用父进程的wait_sema，因为给父进程up的thread可能不是父进程想等的thread
  sema_down(&(temp->wait_sema));
  int code = temp->exit_code;
  // 获取到子进程退出码，通知子进程可以继续销毁
  sema_up(&temp->wait_code_sema);
  return code;
}

/* Free the current process's resources. */
void process_exit(void)
{
  struct thread *cur = thread_current();
  uint32_t *pd;

  /* 打印退出码 */
  // printf("%s: exit(%d)\n", thread_name(), cur->exit_code);

  // sema_up(&(thread_current()->wait_sema));

  /* Destroy the current process's page directory and switch back
     to the kernel-only page directory. */
  pd = cur->pagedir;
  if (pd != NULL)
  {
    /* Correct ordering here is crucial.  We must set
         cur->pagedir to NULL before switching page directories,
         so that a timer interrupt can't switch back to the
         process page directory.  We must activate the base page
         directory before destroying the process's page
         directory, or our active page directory will be one
         that's been freed (and cleared). */
    cur->pagedir = NULL;
    pagedir_activate(NULL);
    pagedir_destroy(pd);
  }
}

/* Sets up the CPU for running user code in the current
   thread.
   This function is called on every context switch. */
void process_activate(void)
{
  struct thread *t = thread_current();

  /* Activate thread's page tables. */
  pagedir_activate(t->pagedir);

  /* Set thread's kernel stack for use in processing
     interrupts. */
  tss_update();
}

/* We load ELF binaries.  The following definitions are taken
   from the ELF specification, [ELF1], more-or-less verbatim.  */

/* ELF types.  See [ELF1] 1-2. */
typedef uint32_t Elf32_Word, Elf32_Addr, Elf32_Off;
typedef uint16_t Elf32_Half;

/* For use with ELF types in printf(). */
#define PE32Wx PRIx32 /* Print Elf32_Word in hexadecimal. */
#define PE32Ax PRIx32 /* Print Elf32_Addr in hexadecimal. */
#define PE32Ox PRIx32 /* Print Elf32_Off in hexadecimal. */
#define PE32Hx PRIx16 /* Print Elf32_Half in hexadecimal. */

/* Executable header.  See [ELF1] 1-4 to 1-8.
   This appears at the very beginning of an ELF binary. */
struct Elf32_Ehdr
{
  unsigned char e_ident[16];
  Elf32_Half e_type;
  Elf32_Half e_machine;
  Elf32_Word e_version;
  Elf32_Addr e_entry;
  Elf32_Off e_phoff;
  Elf32_Off e_shoff;
  Elf32_Word e_flags;
  Elf32_Half e_ehsize;
  Elf32_Half e_phentsize;
  Elf32_Half e_phnum;
  Elf32_Half e_shentsize;
  Elf32_Half e_shnum;
  Elf32_Half e_shstrndx;
};

/* Program header.  See [ELF1] 2-2 to 2-4.
   There are e_phnum of these, starting at file offset e_phoff
   (see [ELF1] 1-6). */
struct Elf32_Phdr
{
  Elf32_Word p_type;
  Elf32_Off p_offset;
  Elf32_Addr p_vaddr;
  Elf32_Addr p_paddr;
  Elf32_Word p_filesz;
  Elf32_Word p_memsz;
  Elf32_Word p_flags;
  Elf32_Word p_align;
};

/* Values for p_type.  See [ELF1] 2-3. */
#define PT_NULL 0           /* Ignore. */
#define PT_LOAD 1           /* Loadable segment. */
#define PT_DYNAMIC 2        /* Dynamic linking info. */
#define PT_INTERP 3         /* Name of dynamic loader. */
#define PT_NOTE 4           /* Auxiliary info. */
#define PT_SHLIB 5          /* Reserved. */
#define PT_PHDR 6           /* Program header table. */
#define PT_STACK 0x6474e551 /* Stack segment. */

/* Flags for p_flags.  See [ELF3] 2-3 and 2-4. */
#define PF_X 1 /* Executable. */
#define PF_W 2 /* Writable. */
#define PF_R 4 /* Readable. */

static bool setup_stack(void **esp);
static bool validate_segment(const struct Elf32_Phdr *, struct file *);
static bool load_segment(struct file *file, off_t ofs, uint8_t *upage,
                         uint32_t read_bytes, uint32_t zero_bytes,
                         bool writable);

static void push_argvii(char *words, void **esp)
{
  char *i;
  i = strtok_r(NULL, " ", &words); //取出words中的第一个参数给i，剩下的重新赋给words从而实现递归
  if (i == NULL)
    return;
  push_argvii(words, esp); //递归

  push_string_argvii(i, esp);
  //*(i + strlen(i)) = '\0';
}
//放入参数字符串
static void push_string_argvii(char *str, void **esp)
{
  *esp -= strlen(str) + 1;
  memcpy(*esp, str, strlen(str) + 1);
}

//放入空白符align：保证argv[argc]的地址是4的倍数，又因为下面都是指针或int类型，从而保证return address是4的倍数
static void push_align(void **esp)
{
  while ((uint32_t)*esp % 4 != 0)
    *esp -= 1;
}

static void push_argvi(char *words, void **esp, uint32_t *temp_esp, uint32_t *num_p)
{
  char *i;
  i = strtok_r(NULL, " ", &words);
  if (i == NULL)
    return;
  push_argvi(words, esp, temp_esp, num_p);
  *num_p += 1; // num_p是参数个数num的指针，非指针类型无法递归传参
  *temp_esp -= strlen(i) + 1;
  push_address_argvi(esp, temp_esp);
  //*(i + strlen(i)) = '\0';
}
//放入address和argv、argc、return address，都是4字节

static void push_address_argvi(void **esp, uint32_t *address)
{
  *esp -= sizeof(uint32_t);
  memcpy(*esp, address, sizeof(uint32_t));
}

/* Loads an ELF executable from FILE_NAME into the current thread.
   Stores the executable's entry point into *EIP
   and its initial stack pointer into *ESP.
   Returns true if successful, false otherwise. */
bool load(const char *file_name, void (**eip)(void), void **esp)
{
  struct thread *t = thread_current();
  struct Elf32_Ehdr ehdr;
  struct file *file = NULL;
  off_t file_ofs;
  bool success = false;
  int i;

  /* Allocate and activate page directory. */
  t->pagedir = pagedir_create();
  if (t->pagedir == NULL)
    goto done;
  process_activate();

  /* 分词 */
  char *first; // 第0个参数
  char *words; // 剩余参数
  char *temp_file_name = file_name;
  int len = strlen(temp_file_name);
  first = strtok_r(temp_file_name, " ", &words);

  /* Open executable file. */
  file = filesys_open(file_name);

  if (file == NULL)
  {
    printf("load: %s: open failed\n", file_name);
    goto done;
  }

  t->exec_file = file;

  /* 禁止对该文件的写操作 */
  file_deny_write(file);

  /* Read and verify executable header. */
  if (file_read(file, &ehdr, sizeof ehdr) != sizeof ehdr || memcmp(ehdr.e_ident, "\177ELF\1\1\1", 7) || ehdr.e_type != 2 || ehdr.e_machine != 3 || ehdr.e_version != 1 || ehdr.e_phentsize != sizeof(struct Elf32_Phdr) || ehdr.e_phnum > 1024)
  {
    printf("load: %s: error loading executable\n", file_name);
    goto done;
  }

  /* Read program headers. */
  file_ofs = ehdr.e_phoff;
  for (i = 0; i < ehdr.e_phnum; i++)
  {
    struct Elf32_Phdr phdr;

    if (file_ofs < 0 || file_ofs > file_length(file))
      goto done;
    file_seek(file, file_ofs);

    if (file_read(file, &phdr, sizeof phdr) != sizeof phdr)
      goto done;
    file_ofs += sizeof phdr;
    switch (phdr.p_type)
    {
    case PT_NULL:
    case PT_NOTE:
    case PT_PHDR:
    case PT_STACK:
    default:
      /* Ignore this segment. */
      break;
    case PT_DYNAMIC:
    case PT_INTERP:
    case PT_SHLIB:
      goto done;
    case PT_LOAD:
      if (validate_segment(&phdr, file))
      {
        bool writable = (phdr.p_flags & PF_W) != 0;
        uint32_t file_page = phdr.p_offset & ~PGMASK;
        uint32_t mem_page = phdr.p_vaddr & ~PGMASK;
        uint32_t page_offset = phdr.p_vaddr & PGMASK;
        uint32_t read_bytes, zero_bytes;
        if (phdr.p_filesz > 0)
        {
          /* Normal segment.
                     Read initial part from disk and zero the rest. */
          read_bytes = page_offset + phdr.p_filesz;
          zero_bytes = (ROUND_UP(page_offset + phdr.p_memsz, PGSIZE) - read_bytes);
        }
        else
        {
          /* Entirely zero.
                     Don't read anything from disk. */
          read_bytes = 0;
          zero_bytes = ROUND_UP(page_offset + phdr.p_memsz, PGSIZE);
        }
        if (!load_segment(file, file_page, (void *)mem_page,
                          read_bytes, zero_bytes, writable))
          goto done;
      }
      else
        goto done;
      break;
    }
  }

  /* Set up stack. */
  if (!setup_stack(esp))
    goto done;

  char *cpy = malloc(strlen(words) + 1);
  memcpy(cpy, words, strlen(words) + 1);
  /* 参数入栈 */
  uint32_t temp_esp = (uint32_t)*esp;
  // 放入参数字符串
  push_argvii(words, esp);        //放入words
  push_string_argvii(first, esp); //放入第0个参数
  //*(temp_file_name + len) = '\0';

  //存入空白符align
  push_align(esp);

  uint32_t num = 0;
  //放入参数字符串地址
  push_address_argvi(esp, &num);         //放入argv[argc] = 0
  push_argvi(cpy, esp, &temp_esp, &num); //放入words的地址
  num++;
  temp_esp -= strlen(first) + 1;
  push_address_argvi(esp, &temp_esp); //放入第0个参数first
  //*(temp_file_name + len) = '\0';

  //放入argv
  temp_esp = (uint32_t)*esp;
  push_address_argvi(esp, &temp_esp);
  //放入argc
  push_address_argvi(esp, &num);
  //放入return address
  num = 0;
  push_address_argvi(esp, &num);

  /* Start address. */
  *eip = (void (*)(void))ehdr.e_entry;

  success = true;
  free(cpy);
done:
  /* We arrive here whether the load is successful or not. */

  return success;
}

/* load() helpers. */

static bool install_page(void *upage, void *kpage, bool writable);

/* Checks whether PHDR describes a valid, loadable segment in
   FILE and returns true if so, false otherwise. */
static bool
validate_segment(const struct Elf32_Phdr *phdr, struct file *file)
{
  /* p_offset and p_vaddr must have the same page offset. */
  if ((phdr->p_offset & PGMASK) != (phdr->p_vaddr & PGMASK))
    return false;

  /* p_offset must point within FILE. */
  if (phdr->p_offset > (Elf32_Off)file_length(file))
    return false;

  /* p_memsz must be at least as big as p_filesz. */
  if (phdr->p_memsz < phdr->p_filesz)
    return false;

  /* The segment must not be empty. */
  if (phdr->p_memsz == 0)
    return false;

  /* The virtual memory region must both start and end within the
     user address space range. */
  if (!is_user_vaddr((void *)phdr->p_vaddr))
    return false;
  if (!is_user_vaddr((void *)(phdr->p_vaddr + phdr->p_memsz)))
    return false;

  /* The region cannot "wrap around" across the kernel virtual
     address space. */
  if (phdr->p_vaddr + phdr->p_memsz < phdr->p_vaddr)
    return false;

  /* Disallow mapping page 0.
     Not only is it a bad idea to map page 0, but if we allowed
     it then user code that passed a null pointer to system calls
     could quite likely panic the kernel by way of null pointer
     assertions in memcpy(), etc. */
  if (phdr->p_vaddr < PGSIZE)
    return false;

  /* It's okay. */
  return true;
}

/* Loads a segment starting at offset OFS in FILE at address
   UPAGE.  In total, READ_BYTES + ZERO_BYTES bytes of virtual
   memory are initialized, as follows:

        - READ_BYTES bytes at UPAGE must be read from FILE
          starting at offset OFS.

        - ZERO_BYTES bytes at UPAGE + READ_BYTES must be zeroed.

   The pages initialized by this function must be writable by the
   user process if WRITABLE is true, read-only otherwise.

   Return true if successful, false if a memory allocation error
   or disk read error occurs. */
static bool
load_segment(struct file *file, off_t ofs, uint8_t *upage,
             uint32_t read_bytes, uint32_t zero_bytes, bool writable)
{
  ASSERT((read_bytes + zero_bytes) % PGSIZE == 0);
  ASSERT(pg_ofs(upage) == 0);
  ASSERT(ofs % PGSIZE == 0);

  file_seek(file, ofs);
  while (read_bytes > 0 || zero_bytes > 0)
  {
    /* Calculate how to fill this page.
         We will read PAGE_READ_BYTES bytes from FILE
         and zero the final PAGE_ZERO_BYTES bytes. */
    size_t page_read_bytes = read_bytes < PGSIZE ? read_bytes : PGSIZE;
    size_t page_zero_bytes = PGSIZE - page_read_bytes;

    // changed
    if (!page_new_file(&thread_current()->page_table, thread_current(),
                       upage, writable,
                       file, file_tell(file), page_read_bytes))
      return false;
    file_seek(file, file_tell(file) + page_read_bytes);

    // /* Get a page of memory. */
    // uint8_t *kpage = palloc_get_page(PAL_USER);
    // if (kpage == NULL)
    //   return false;

    // /* Load this page. */
    // if (file_read(file, kpage, page_read_bytes) != (int)page_read_bytes)
    // {
    //   palloc_free_page(kpage);
    //   return false;
    // }
    // memset(kpage + page_read_bytes, 0, page_zero_bytes);

    // /* Add the page to the process's address space. */
    // if (!install_page(upage, kpage, writable))
    // {
    //   palloc_free_page(kpage);
    //   return false;
    // }

    /* Advance. */
    read_bytes -= page_read_bytes;
    zero_bytes -= page_zero_bytes;
    upage += PGSIZE;
  }
  return true;
}

/* 为进程分配起始的栈
每个进程的虚拟地址都是从PHYS_BASE开始的*/
static bool
setup_stack(void **esp)
{
  bool success = false;
  // 新建一个存放stack的page，虚拟地址是第一页
  page_new_stack(&thread_current()->page_table, thread_current(), (uint8_t *)PHYS_BASE - PGSIZE);
  // 给page分配物理地址
  success = frame_reload_page((uint8_t *)PHYS_BASE - PGSIZE);
  if (success)
    *esp = PHYS_BASE; // 让栈顶指针esp指向栈顶PHYS_BASE
  return success;
}
